Course: Earth Science Unit: Stars Topic: Parallax - Measuring Distances in Space
Instructional Objectives:
Students will be able to
Define and explain what stellar parallax is
Explain how astronomers use parallax to measure the distances of stars
Determine the relationship between the distance to the object being observed and the distance between two points of observation
Investigate the effect of distance to the object and the baseline on parallax
Draw conclusions from observations and collected data
Intro:
In the previous lesson students observed how distance was an external factor that affected the apparent brightness of a star. In this lesson students are going to learn how astronomers use stellar parallax to determine the distances of space objects. During the lesson students will be able to explore the effect of parallax on objects of varying differences in order to determine the relationship between the distance to the object being observed and the distance between two points of observation. Students will be asked how they think astronomers can measure the distances of stars from earth. Students will briefly discuss their ideas. After the discussion, the teacher will explain parallax by having students hold up their index finger at arms length at look at it with one eye open alternating each eye. The change is position they observe is what is called parallax. Students will experiment with this by moving their finger closer to their eyes, still alternating between the right and left eyes. They will notice that the change in the shift is greater.
Body:
During the first activity students will determine the effect of parallax of the distance of an object from an observer. Prior to class, the teacher will have drawn a series of equally spaced vertical lines 3 centimeters apart across the chalkboard numbered from 1-20. The teacher will also pass out their data tables for the activity. A student volunteer will stand about 2.1m away from the board holding up a pencil at arms length. Each student will take a turn standing away form the student at distances of 1 meter, 2 meters, and 3 meters. The teacher will make 2 stations at each distance away fro the board. At each distance the students will close their right eye and look at the pencil with their left. They will mark the number at which they see the pencil at against the board. Then they will do the same thing except they will close their left eye and view the pencil with their right marking the number at board on their tables. Once this is done students will take the number of the first observation and minus the number from the second observation to determine the parallax.
In the second activity students will determine the effect on parallax of the distance between two points of observation – the baseline. Students will be put into groups of three. Using the same ruler on the chalkboard each group will be given a cardboard square with four holes punched in them (15cm between each hole). One student from each group will stand 3m from the chalkboard holding the cardboard square. The second member will be standing about 1.5m from the chalkboard holding the pencil. The third member will be looking through each hole in the cardboard and recording the number where they see the pencil in reference to the numbers on the board. After students will review their data from the two activities and answer the questions on their sheet.
Conclusion:
After students are finished the teacher will go over the answers to the questions and discuss the class’ observations and findings about parallax. For each question the teacher will ask for the students’ answers and discuss their reasoning before providing the correct answers and explanations. To end the class students will discuss why the rotation of the earth makes it easy for astronomers to determine the parallax shift and how the parallax to any stellar object can be found. By the end of the lesson students should have a basic understanding that parallax is the apparent shifting of an object when viewed against a stationary background from two different points and that astronomers use it to determine the distance of space objects. Students will also be able to link this lesson to the previous one by already knowing that distance between stars and Earth affects the apparent magnitude of star seen by us on Earth.
Assessment:
Students will be assesed by:
Their ability to explain and describe what parallax is
Their ability to explain how astronomer determine the parallax of space objects
The completion of the in class worksheet
Answering worksheet questions based on the observations of the in class acitivities
Unit: Stars
Topic: Parallax - Measuring Distances in Space
Instructional Objectives:
Students will be able to
Intro:
In the previous lesson students observed how distance was an external factor that affected the apparent brightness of a star. In this lesson students are going to learn how astronomers use stellar parallax to determine the distances of space objects. During the lesson students will be able to explore the effect of parallax on objects of varying differences in order to determine the relationship between the distance to the object being observed and the distance between two points of observation. Students will be asked how they think astronomers can measure the distances of stars from earth. Students will briefly discuss their ideas. After the discussion, the teacher will explain parallax by having students hold up their index finger at arms length at look at it with one eye open alternating each eye. The change is position they observe is what is called parallax. Students will experiment with this by moving their finger closer to their eyes, still alternating between the right and left eyes. They will notice that the change in the shift is greater.
Body:
During the first activity students will determine the effect of parallax of the distance of an object from an observer. Prior to class, the teacher will have drawn a series of equally spaced vertical lines 3 centimeters apart across the chalkboard numbered from 1-20. The teacher will also pass out their data tables for the activity. A student volunteer will stand about 2.1m away from the board holding up a pencil at arms length. Each student will take a turn standing away form the student at distances of 1 meter, 2 meters, and 3 meters. The teacher will make 2 stations at each distance away fro the board. At each distance the students will close their right eye and look at the pencil with their left. They will mark the number at which they see the pencil at against the board. Then they will do the same thing except they will close their left eye and view the pencil with their right marking the number at board on their tables. Once this is done students will take the number of the first observation and minus the number from the second observation to determine the parallax.
In the second activity students will determine the effect on parallax of the distance between two points of observation – the baseline. Students will be put into groups of three. Using the same ruler on the chalkboard each group will be given a cardboard square with four holes punched in them (15cm between each hole). One student from each group will stand 3m from the chalkboard holding the cardboard square. The second member will be standing about 1.5m from the chalkboard holding the pencil. The third member will be looking through each hole in the cardboard and recording the number where they see the pencil in reference to the numbers on the board. After students will review their data from the two activities and answer the questions on their sheet.
Conclusion:
After students are finished the teacher will go over the answers to the questions and discuss the class’ observations and findings about parallax. For each question the teacher will ask for the students’ answers and discuss their reasoning before providing the correct answers and explanations. To end the class students will discuss why the rotation of the earth makes it easy for astronomers to determine the parallax shift and how the parallax to any stellar object can be found. By the end of the lesson students should have a basic understanding that parallax is the apparent shifting of an object when viewed against a stationary background from two different points and that astronomers use it to determine the distance of space objects. Students will also be able to link this lesson to the previous one by already knowing that distance between stars and Earth affects the apparent magnitude of star seen by us on Earth.
Assessment:
Students will be assesed by:
Sources:
Smith, S (2001). Project Earth Science: Astronomy. Arlington, Virginia: NSTA Press.
Teacher Resources:
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